CuZnAl水滑石衍生催化剂上甲醇水蒸气重整制氢Ⅰ. 催化剂焙烧温度的影响

 以类层柱CuZnAl水滑石为前体,经不同温度焙烧制备了一系列甲醇水蒸气重整制氢催化剂. 在250 ℃、 水/甲醇比1.3和重时空速2.5 h-1下的反应结果表明, 600 ℃焙烧的催化剂具有优异的活性和稳定性,而≤500 ℃和≥700 ℃焙烧后的催化剂活性较差. 热重、 X射线衍射、 傅里叶变换红外光谱和程序升温还原分析结果表明, 600 ℃焙烧时水滑石分解较为完全,析出纳米CuO粒子的同时伴生CuAl2O4尖晶石相,进而在反应过程中对金属Cu纳米粒子和ZnO起到良好的隔离和稳定作用. 焙烧温度≥700 ℃时CuO纳米粒子发生二次团聚,同时CuAl2O4尖晶石相大量生成,造成催化活性位减少,活性较低; 而焙烧温度≤500 ℃时水滑石分解不完全,生成 (Cu,Zn)AlxOy(CO3)z复合物且无尖晶石相伴生,造成反应中金属Cu纳米粒子和ZnO聚集,导致催化剂活性较低.     

La0.8Sr0.2Ga0.8Mg0.2O3与La0.8Sr0.2Ga0.8Mg0.15Co0.05O3电导的对比

采用固相合成法制备了La0.8Sr0.2Ga0.8Mg0.2O3(LSGM8282)和La0.8Sr0.2Ga0.8Mg0.15Co0.05O3 (LSGMC5), 利用四电极交流阻抗法和Hebb-Wagner 极化法对比研究了两种材料的总电导率和电子电导率. 实验结果表明, LSGM8282 的总电导率与氧分压无明显依赖关系, 而LSGMC5 的总电导率在高氧分压区随氧分压降低而增加,在中等氧分压区域基本保持不变. 在973-1173 K的温度范围内, LSGM8282的自由电子电导率以及电子空穴电导率的氧分压级数分别为-1/4和1/4.在1073-1173 K的温度范围内, LSGMC5的自由电子电导率以及电子空穴电导率的氧分压级数分别为-1/4和约为1/8, 表明LSGMC5的空穴产生机制可能与LSGM8282不同. LSGM8282 的氧离子电导率与氧分压无关, 而LSGMC5 的氧离子电导率在高氧分压区随氧分压的减小而增加.     

面粉中滑石粉的X射线衍射分析

通过四氯化碳分离或高温灰化,X射线衍射分析测定面粉中掺入的滑石粉。其中灰化处理适宜温度为500~750℃。该方法简便、快速,灵敏度高,样品用量少,准确可靠,可推广为检测面粉质量的一种较理想的手段。     

单链和寡链等规聚苯乙烯聚集体的结晶行为

自1960年Hoffman等提出聚合物结晶成核理论以来,人们对聚合物结晶生长速率、片晶的侧向尺寸随过冷度的变化等现象成功地进行了理论描述．1997年,Hoffman等对聚合物结晶成核理论进行修正,将de Gennes的聚合物“蛇行”概念。引入表面成核理论,通过对单根分子链从过冷熔体“卷绕”到晶体前沿所需的时间进行估算,其结果远远低于Flory预言时间约3～5个数量级,据此,Hoff-man认为,在聚合物结晶过程中,分子链在强迫稳态下的“蛇行”运动有足够的时间解缠结和结晶。     

微波辅助萃取新鲜芦荟叶中芦荟甙的研究

应用密闭微波萃取装置对芦荟中的有效成分芦荟甙进行了微波萃取研究,并利用透射电子显微镜对微波萃取机理进行了初步探讨.讨论了不同萃取剂、溶剂浓度、萃取时间和微波功率等对提取率的影响.在萃取剂为乙醇-水体系,溶剂(乙醇)体积分数为70%、萃取时间为4min及微波功率为340W的条件下,萃取效果最佳.与索氏提取及超声波萃取法相比,本法具有萃取速度快、提取率高及溶剂用量少等特点.     

活性碳纤维阴极电芬顿反应降解微囊藻毒素研究

以具有高比表面积的活性碳纤维作为阴极,通过电芬顿反应降解水中微囊藻毒素(MCRR,MCLR)的电化学方法系统考察了电流密度、pH值和Fe2+浓度等因素对微囊藻毒素降解效果的影响.实验结果表明,在Fe2+浓度为1.0mmol/L和电流密度为6.6mA/cm2条件下,电化学处理60min,MCRR(8.81mg/L)去除率为75%,MCLR(6.36mg/L)去除率为94%.证明过氧化氢可以通过电化学还原在活性碳纤维阴极表面高效产生,微囊藻毒素可被高效降解去除.     

Octyl-type monolithic columns of 530 microm i.d. for capillary liquid chromatography

A novel monolithic capillary column (530 microm i.d.) was prepared for capillary liquid chromatography (CLC) by in situ copolymerization of octyl methacrylate (MAOE) and ethylene dimethacrylate (EDMA) in the presence of a porogen solvent containing 1-propanol, 1,4-butanediol, and water with azobisisobutyronitrile as the initiator. The influences of the contents of the porogen solvent, EDMA and the various concentration ratios of 1-propanol to 1,4-butanediol in the polymerization mixture on the morphology, porosity, globule size, stability and column efficiency were investigated. The morphology and pore size distribution of monolithic capillary columns were characterized by SEM and mercury intrusion porosimetry, respectively. Chromatographic evaluations of the columns were performed under CLC mode. The results showed that good permeability and stability can be obtained under optimal experimental conditions. The separation results of some acid, neutral and basic analytes demonstrated the hydrophobicity and low affinity to basic analytes of the new column. Three metal ions, i.e. Mg(II), Zn(II) and Cd(II) were also separated under ion-pair mode on the new monolithic capillary column and the results were acceptable.     

Virtual screening of novel noncovalent inhibitors for SARS-CoV 3C-like proteinase

The SARS coronavirus 3C-like proteinase is considered as a potential drug design target for the treatment of severe acute respiratory syndrome (SARS). Owing to the lack of available drugs for the treatment of SARS, the discovery of inhibitors for SARS coronavirus 3C-like proteinase that can potentially be optimized as drugs appears to be highly desirable. We have built a "flexible" three-dimensional model for SARS 3C-like proteinase by homology modeling and multicanonical molecular dynamics method and used the model for virtual screening of chemical databases. After Dock procedures, strategies including pharmocophore model, consensus scoring, and "drug-like" filters were applied in order to accelerate the process and improve the success rate of virtual docking screening hit lists. Forty compounds were purchased and tested by HPLC and colorimetric assay against SARS 3C-like proteinase. Three of them including calmidazolium, a well-known antagonist of calmodulin, were found to inhibit the enzyme with an apparent K(i) from 61 to 178 microM. These active compounds and their binding modes provide useful information for understanding the binding sites and for further selective drug design against SARS and other coronavirus.     

钛酸铅和钛酸钡振动性质及铁电相变的密度泛函理论研究

采用密度泛函赝势的方法, 研究了不同晶相的钛酸铅和钛酸钡的振动模式. 没有发现钛酸铅存在低温相变的证据, 而钛酸钡则存在四方-正交和正交-三角铁电相变. 振动频率随四方应变的变化关系表明, 随着四方应变的增大, 软模的频率增大, 在某一个临界点, 不稳定的软模转变为稳定的振模. 由于钛酸铅具有较大的四方应变, 使得其能够在四方相稳定下来, 而钛酸钡较小的四方应变是其仍能够发生低温铁电相变的一个重要原因.     

钒钼磷杂多酸催化苯直接羟化为苯酚的动力学研究

以钒钼磷杂多酸作为催化剂,用紫外可见分光光度法研究了过氧化氢直接将苯氧化羟基化为苯酚反应的动力学行为。结果表明,该氧化羟化反应速率对底物苯、氧化剂和催化剂都是一级反应,反应的活化能为57.73kJ.mol-1。本文推测了杂多酸配合物催化苯氧化羟化为苯酚反应的过程,建立了该反应动力学数学模型,模型很好地解释了实验结果。